Vascular clamps play a vital and obvious role during surgery, their task being complete vascular occlusion by squeezing the blood vessel between the two jaws of a clamp or a forceps. The process of clamping generates loci of extremely high pressure far in excess of the pressure in the blood vessel itself and are apt to cause serious injury to all layers of the vessel. The generally used clamps such as the Fogarty Clamp, the De Bakey "Atraugrip", the Bulldog Clamp, or Pott's and Satinsky's peripheral vascular clamps exert very high pressures, of up to 9 bar, on the clamped blood vessel and have caused intimal to major medial damage commencing at a pressure of 2.5 bar.
The clinical consequences of vascular injury have not always received sufficient attention, but a few fatal outcomes have been reported which were actually due to clamp injuries. Less obvious damage may cause the eventual attrition of blood vessels by an injury sufficient to cause endothelial desquamation associated with fragmentation of the internal elastic lamina and smooth muscle hyperplasia in the media and formation of an intimal thickening or fibrous plaque.
Clamp-induced damage may have dire consequences to the patient, an important case being that of the early and intermediate fate of aorta-coronary by-pass surgery using reversed saphenous vein. About 150,000 such operations are performed annually in the U.S.A. alone, and the results show an attrition rate of from 5 to 10% for the first year, mainly attributed to thrombosis, 2% per annum during the next six years, associated with intinal hyerplasia due to vascular damage, and 5% per annum for the following 5 years. Thus, even in elite institutions as much as 24% of by-pass surgery may fail owing to iatrogenic vascular damage caused by trauma inflicted during the operation.
In view of the fact that systemic blood pressure is at least one order of magnitude lower than the pressure applied to the blood vessel by the conventional clamps, it becomes evident that vascular occlusion could be achieved at far lower pressures than hitherto applied. An appropriate method of properly blocking the blood flow in a vessel while avoiding localized loci of excessive pressure would be to surround the blood vessel with a uniform external pressure field, analogous to the way in which a blood pressure cuff works.
In recent years it has been tried to replace the rigid and hard clamp surfaces by bodies of soft and resilient material, but those known at present are not feasible for forming an eternal uniform pressure field around the blood vessel, which is the foremost aim of the present invention. These clamps show a certain improvement over the conventional rigid and hard clamps, but all suffer from the drawback that they do not exert uniform, relatively low pressure on the entire circumference of the blood vessel. A few examples are given in the following:
U.S. Pat. No. 4,531,519 (DUNN) discloses a vascular clamp in the form of a tapering, flexible and tubular envelope which is wound around the blood vessel to be occluded and is inflated by air or another fluid.
U.S. Pat. No. 5,152,770 (BENGMARK) describes a similar device which includes a flexible, elongate strip covered on its one side with a plurality of communicating bulbs. The strip is wound around the blood vessel or duct to be occluded and the bulbs are inflated to a pressure serving to occlude the duct. After deflation of the bulbs the strip is removed to allow the duct to re-open. As in the vascular clamp escibed in DUNN, the application of the strip or envelope by winding it around the blood vessel and subsequently inflating it until the flow of blood or other body fluid is stopped, is a difficult and time consuming task. For this reason both devices are used in exceptional cases only.
U.S. Pat. No. 5,282,812 (SUAREZ) discloses a vascular clamp in the form of a strip of metal bent into V-shape with its inside surfaces lined with a resilient material. Closing of a vessel is described, whereby the clamp is to be held in a forceps, to be pushed over the vessel to be occluded and pressed onto the vessel, whereafter the forceps is removed. The material of the strip is supposed to keep its shape after removal of the forceps and to maintain the necessary pressure during the operation. The device is provided with means for engaging the forceps jaws after completed surgery for opening the V and for removing the clamp. It is claimed that the strip material would have a positional memory for exerting the necessary pressure after positioning. This would require a different size and material of the device for every size of vessel and blood pressure.
Canadian Patent No.1103119 (MUERMANS) discloses a surgical clamp having two clamping jaws and comprising a soft pad placed over each jaw. Each pad includes two cavities, one of them tightly located over the respective jaw, the second cavity is filled with a fluid or solid and is subsequently sealed. It is claimed that the device clamps the vessel without damage.
In fact the vessel is clamped between two long surfaces which are soft and resilient, but the effect is equal to the squeezing of the vessel from two opposite directions only without exerting uniform pressure on the entire circumference, which is the aim of the present clamp.
In short, the above described clamps do not fulfill the requirements of occlusion of a blood vessel or any other duct in a living body without damaging it, while the objects of the present invention are as follows:
1. a vascular clamp provided with two compliant and stretchable surfaces surrounding the blood vessel on all sides, PA1 2. a vascular clamp exerting a uniform circumferential pressure field, PA1 3. a vascular clamp exerting an invariant pressure on the vessel during the entire operation, PA1 4. a vascular clamp provided with disposable clamping surfaces.
A vascular clamp permitting the exchange of its clamping surfaces to adapt the clamp to different application in respect of specific blood vessels or ducts.